The present invention relates to processing methods and apparatus for converting coal or other coal-bearing materials into char. Char can be produced by heating coal or other coal-bearing materials to selected temperatures in a reduced-oxygen environment. Char having suitable properties may be used in, among other things, iron and steel processing furnaces.
Heating coal or other coal-bearing materials in a reduced-oxygen environment produces coal gas, volatile liquids and a residue of char. During the process of making char, volatile materials, such as hydrocarbon fuels, in the coal-bearing materials fluidize when heated to a temperature of approximately 650° F. (approximately 350° C.) and higher.
A pyrolyzer furnace is one apparatus that may be used for processing coal and other hydrocarbon materials into char. A pyrolyzer can operate in a batch or in a continuous process. In one continuous pyrolyzer, one or more drive screws rotate within the pyrolyzer furnace, wherein the coal is heated in a reduced-oxygen environment to a temperature to fluidize the volatile material as the coal-bearing materials are moved through the furnace. An example of a continuous pyrolyzer furnace is disclosed in U.S. Pat. No. 5,151,159 to Wolfe, et al. Previous pyrolyzer furnaces disclosed by the prior art had heating elements positioned within the furnace housing, which generated hot spots within the furnace, caused uneven heating of the coal or other coal-bearing material, and caused fatigue and shortened the life of the furnace components.
Another limitation has been the energy efficiency of previous pyrolyzer furnaces. The previous pyrolyzer furnaces were typically heated by electric heaters, or by burning natural gas, fuel oil or propane, to process the fluidized volatile material into hydrocarbon fuel and coal tar products. Pyrolyzer furnaces in the prior art also had drive screws with solid shafts, oil cooled shafts, and other shaft configurations that were thermally inefficient, resulting in the pyrolyzer furnace consuming more fuel.
What has been needed is a pyrolyzer furnace system, and method for making char in that system, that substantially reduces the external energy, e.g. propane, fuel oil, or natural gas, needed for the char making process. The level of additional energy may be reduced to a point that the char making process is sustained by burning only the fluidized volatile materials generated from char making after start up.
Disclosed is a char making apparatus comprising:                a longitudinal pyrolyzer furnace housing wherein coal-bearing material containing volatile materials may be heated to a temperature to fluidize volatile materials therein and plasticize coal in the coal-bearing material;        at least two rotatable drive screws laterally positioned and interleaved within the longitudinal furnace housing and capable of conveying coal-bearing materials containing volatile material through the pyrolyzer furnace housing, each drive screw having a hollow drive shaft and a diverter longitudinally positioned within the drive shaft, the diverter forming with an inner surface of each drive shaft an inner passageway to provide heat flux from the combustion fluid moving through the shaft to adjacent coal-bearing materials moving through the pyrolyzer furnace to enable fluidizing the volatile material therein and plasticizing coal in the coal bearing material;        a heating jacket about the longitudinal furnace housing along at least a portion thereof in fluid communication with combustion fluid from multiple combustion chambers to provide heat flux from the combustion fluid moving through the heating jacket to heat adjacent coal-bearing materials moving through the pyrolyzer furnace to fluidize the volatile material in the coal bearing material and plasticize the coal in the coal bearing material;        multiple combustion chambers adjacent the inner passageways and adjacent the heating jacket capable of burning fluidized combustion material and exhausting combustion fluids through the inner passageway and through the heating jacket to fluidized volatile material in the coal-bearing material and plasticizing coal in the coal-bearing material; and        conduit capable of collecting and transferring fluidized volatile material exhausted from the pyrolyzer furnace to the combustion chambers to be burned.        
The flow of combustion fluids through the inner passageways within the hollow drive screws may be in the same direction as the drive screws move the coal-bearing materials through the pyrolyzer furnace housing.
Also, the combustion chambers are spaced along the pyrolyzer furnace housing to distribute the combustion fluid moving from such combustion chambers through the heating jacket to exhaust ports from pyrolyzer furnace housing to provide a desired pattern of heat flux from the combustion fluid to the adjacent coal-bearing material moving through the pyrolyzer furnace housing.
Flow controllers may be positioned in the heating jacket and are capable of diverting the flow of combustion fluid through said heating jacket to provide a desired heat flux pattern to fluidize volatile material in the coal bearing material and plasticize coal in the coal bearing material.
Devices may also be positioned in the inner passageways and are capable of causing the flow of heated fluid through the passageway to have a Reynolds Number greater than 4000.
The portion of the pyrolyzer furnace housing downstream through which the coal bearing material moves may have a decreasing cross sectional area in the direction of travel of the coal-bearing material through the pyrolyzer furnace housing to compact the char before exiting the pyrolyzer furnace housing. Or, the pyrolyzer furnace housing may have a tapered outer wall downstream forming a decreasing cross-sectional area of the portion of the pyrolyzer furnace housing through which the coal-bearing material moves in the direction of travel of the coal bearing material through the pyrolyzer furnace housing to compact the char before exiting the pyrolyzer furnace housing.
The hollow drive shaft through each screw may be tapered; decreasing the cross sectional area of the portion of the pyrolyzer furnace housing through which the coal-bearing material moves in the direction of travel of the coal-bearing material through the pyrolyzer furnace housing to compact the char before exiting the pyrolyzer furnace housing.
Alternatively, the pyrolyzer furnace housing may have tapered inner walls and the hollow drive shafts of the drive screws may have tapered outer walls coordinated to decrease the cross sectional area of the portion of the pyrolyzer furnace housing through which the coal-bearing material moves in the direction of travel of the coal-bearing material through the pyrolyzer furnace to compact the char before exiting the pyrolyzer furnace housing.
The heating jacket may surround at least a portion of the pyrolyzer furnace housing, and may surround the pyrolyzer furnace housing substantially along its length.
The char making apparatus may also be capable of fluidizing volatile materials and plasticizing coal in the coal-bearing material to a temperature in a range of 650° F. to 1300° F.
Alternatively the pyrolyzer furnace housing may be inclined at a variable upward angle in the direction of movement of the coal-bearing material through the housing.
At least three drive screws may be laterally positioned within the pyrolyzer furnace housing, the drive screws being positioned such that each drive screw interleaves at least one other drive screw. Further, at least one clearing screw having a smaller diameter may be positioned longitudinally through the furnace housing adjacent the drive screws and may be capable of conveying coal-bearing materials from the drive screws through the pyrolyzer furnace housing.
At least one clearing screw having a smaller diameter may be positioned longitudinally through the furnace housing adjacent the drive screws and capable of conveying coal-bearing materials from the drive screws through the pyrolyzer furnace housing.
Alternatively, the pyrolyzer furnace housing may comprise at least two zones along its length, where the heat flux in the first zone is capable of fluidizing volatile materials, and the second zone is capable of mixing supplemental materials into the coal-bearing materials, and the heat flux in the second and/or subsequent zones is capable of plasticizing coal in the coal-bearing material.
Also, the pyrolyzer furnace housing may comprise at least two zones along its length, where heat flux in the first zone is capable of fluidizing volatile materials, and heat flux in at least one of the subsequent zones are capable of plasticizing coal in the coal-bearing material.
Another char making apparatus is disclosed, comprising:                a longitudinal pyrolyzer furnace housing wherein coal-bearing material containing volatile materials may be heated to a temperature to fluidize volatile materials therein and plasticize coal in the coal bearing material;        at least two rotatable drive screws laterally positioned and interleaved within the longitudinal furnace housing, and capable of conveying coal-bearing materials containing volatile materials through the pyrolyzer furnace housing, each drive screw having a hollow drive shaft and a diverter longitudinally positioned within the drive shaft, the diverter forming with an inner surface of each drive shaft an inner passageway adjacent the coal-bearing materials moving through the pyrolyzer furnace to provide heat flux from the combustion fluid to the coal-bearing material to fluidize the volatile material therein and plasticize coal in the coal bearing material;        double outer walls in the furnace housing at least partially around the rotatable drive screws and forming an outer passageway between the outer walls, the outer passageway capable of moving a combustion fluid adjacent the coal-bearing materials moving through the pyrolyzer furnace housing providing heat flux from the combustion fluid moving through the outer passageways to the coal-bearing material moving through the pyrolyzer furnace housing to fluidize the volatile material in the coal-bearing material and plasticize coal in the coal-bearing material;        multiple combustion chambers adjacent the inner passageway and adjacent the outer passageway capable of burning fluidized combustion material and moving combustion fluids through the inner passageway and the outer passageway to fluidized volatile material in the coal-bearing material and plasticizing coal in the coal-bearing material; and        conduit capable of collecting and transferring fluidized volatile material exhausted from the pyrolyzer furnace to the combustion chambers to be burned.        
Also disclosed is a method for making briquettes comprising the steps of assembling a longitudinal pyrolyzer furnace housing having at least two rotatable drive screws laterally positioned and interleaved within a longitudinal furnace housing and a heating jacket about the longitudinal furnace housing to provide heat flux from combustion fluid moving through the heating jacket to adjacent coal-bearing materials; moving coal-bearing materials through the pyrolyzer furnace by rotation of the drive screws and heating to fluidize volatile material in the coal bearing material and plasticize the coal in the coal bearing material to form processed char; mixing the processed char with a binding agent and a binder coal of a fluidity at least 2,000 ddpm to form a blend of less than 15% binding agent, 25 to 70% processed char and 20 to 70% binder coal; and briquetting the blend to form a briquetted blend that can be carbonized to form metallurgical coke.
Also disclosed is a system for making briquettes comprising a longitudinal pyrolyzer furnace housing having at least two rotatable drive screws laterally positioned and interleaved within the longitudinal furnace housing, and capable of conveying coal-bearing materials containing volatile material through the pyrolyzer furnace housing and a heating jacket about the longitudinal furnace housing along at least a portion thereof in fluid communication with combustion fluid from multiple combustion chambers to provide heat flux from combustion fluid moving through the heating jacket to adjacent coal-bearing materials moving through the pyrolyzer furnace to fluidize the volatile material in the coal bearing material and plasticize the coal in the coal bearing material to produce processed char; a mixer for combining a binder coal having a fluidity of at least 2,000 ddpm, a binder and said processed char in a preferred ratio to form a blend having: less than 15% binding agent, 25 to 70% processed char, and 20 to 70% binder coal; and a briquetter for forming the blend to form a briquette which when carbonized forms a metallurgical coke.